Unless the hole is reamed specifically for a close tolerance application, you'll loose a little joint strength even though the bolt is stronger in shear (and tension). Not knowing the design basis, there's always a little risk with such. A close tolerance application like a HI-LOK fastener would be a better solution than a regular MS fastener.
This will be the third time these parts have been installed - first during the initial build, second when I installed a trutrack-type servo, and now for the GRT servo - I predict that it might happen again, so I'd prefer to not keep drilling out these rivets.Why are you wanting to make the change?
You are probably right. I actually thought that when I installed the original trutrak, since they were the industry standard at that time.I'd suspect you're going to be fine from here on out. The footprint of all the modern servo's from Dynon, Garmin, GRT and even the newer trutrak is nearly identical from what I can tell. With this kind of standardization, I doubt you'd ever have to change the mount again.